Field of the Invention
The present invention relates to a complex protection device, and more particularly to a complex protection device in which both surface-mounted resistive elements and printed resistive elements are installed and thus a circuit and circuit elements installed on the circuit may be protected from overvoltage as well as overcurrent, and the printed resistive elements are disposed under the surface-mounted resistive elements and thus product miniaturization may be achieved.
Description of the Related Art
A non-return type protection device, operated in response to excessive heat generated by overcurrent of a protected apparatus or ambient temperature, is operated at a designated temperature and intercepts an electrical circuit. For example, there is a protection device heating a resistor in response to signal current detecting abnormality of an apparatus and operating a fuse element using generated heat.
Korean Patent Laid-open No. 10-2001-0006916 discloses a protection device in which low melting point metal body electrodes and a heating element are provided on a protection device substrate, a low melting metal body is formed directly on the low melting point metal body electrodes and the heating element, an inner sealing part formed of a solid flux is installed on the low melting metal body so as to prevent surface oxidation of the low melting metal body, and an outer sealing part or a cap to prevent melt from leaking to the outside of the device during breakage of the low melting metal body is installed on the outer surface of the inner sealing part.
FIGS. 11A and 11B illustrate another conventional protection device in which a fusible element (a low melting point metal body) is formed on a resistor (a heating element).
With reference to FIGS. 11A and 11B, in the conventional protection device, a paste-type resistor 2 is applied to a ceramic substrate 1, an insulator 3, fuse terminals 4, a fusible element 5, and a case 6 are sequentially stacked on the resistor 2, and a connection part 4a of the fuse terminal 4 is connected to a resistive terminal 8.
In such a conventional protection device, the fusible element 5 is installed on the resistor 2 and thus, the thickness of the protection device is increased.
Further, since the paste-type resistor 2 is used, the protection device has weak durability insufficient to be applied for high power and is difficult to cope with various environments.